Project Summary. This training grant in developmental endocrinology and metabolism at Children's Hospital Boston intends to provide funding for postdoctoral fellows to engage in research training leading to independent careers in academic pediatric endocrinology. Trainees enter the program with either the MD, MD/PhD or occasionally the PhD degree, and are selected from highly qualified pediatric endocrinology fellows at Children's Hospital. Areas of training include basic investigations in neuroendocrinology, calcium metabolism, carbohydrate pathophysiology, immunoendocrinology, genomic research, thyroid diseases, and bioinformatics, as well as clinical research in obesity, reproductive endocrinology, and carbohydrate metabolism. Training consists of didactic courses, including in quantitative methods and the ethical conduct of research, and an intensive period of individually mentored research. The intended average duration of training is two years. Of the 17 trainees during the past 10 years who have completed this training program, all but 1 are faculty in academic pediatric institutions (1 Associate Professor, 7 Assistant Professors, 8 Instructors). Of these, 7 have had independent NIH K awards, and 1 has an R01. Their record of publication is strong. This program takes advantage of the breadth of scientific expertise of the training faculty within the Division of Endocrinology, as well as in the larger Children's Hospital Boston community and surrounding Harvard environment. The 21 trainers include 9 pediatric endocrine physician-scientists (including 4 MD/PhDs), 9 physician-scientists of other disciplines, and 3 PhD scientists. Children's Hospital is the major training site, along with laboratories at Brigham and Women's Hospital, Massachusetts General Hospital, Beth Israel Deaconess Medical Center, and Joslin Diabetes Center. Relevance. There is a great shortage of qualified pediatrician-scientists in the United States today, at a time when the potential for scientific breakthroughs in the treatment of pediatric diseases like obesity and diabetes is great. These diseases are a great threat to the future health of our nation's children. We hope that our program addresses this need by inspiring the early careers of a highly motivated group of pediatric endocrinology trainees immersed in a rigorous and stimulating learning environment.